What causes persistent swelling in the right supraclavicular

I am 67 and have persistent swelling in the right supraclavicular lymph node. It's larger than a quarter. puffs up quite significantly and causes pain when use my arm a lot. I have had this swelling/pain for several months. I've had an MRI of my shoulder, brevis plexus, and I was sent to a neurologist to look at the disc made of my spine behind my neck, there were issues found but was told none of them could be causing my issues. I'm seeing an ENT in a couple of weeks. I don't know where else to turn at this point. Any ideas what could be causing this?